Tony Bennett and Michael Milken are among those confirmed to attend the event as a feeding frenzy of questions surrounds the frail billionaire, who is turning 92.

This story first appeared in the May 29 issue of The Hollywood Reporter magazine. To receive the magazine, click here to subscribe.

On May 27, Sumner Redstone will turn 92 — an event that will be celebrated by a select circle at the Vibrato Grill Jazz, a restaurant in Bel Air. The party, with a guest list that includes entertainer Tony Bennett and former financier and philanthropist Michael Milken, will take place as a recent flurry of media activity has shined a spotlight, once again, on the fitness and mortality of the man who controls both CBS and Viacom.

Originally, a bigger event was planned to take place on Viacom's Paramount studio lot, but sources say this tribute to Redstone and his "passion to party," as the invitation puts it, was moved to a venue closer to the frail mogul's Beverly Park home — partly because both his live-in girlfriend, Sydney Holland, 43, and his still-close ex-girlfriend, Manuela Herzer, 50, were nervous about the number of people who might try to get close to him. That concern seems to have come from them rather than from Redstone's daughter, Shari. Sources say neither Shari Redstone, 61, nor her three children (including Brandon Korff, with whom Sumner has been close) were invited to the event.

Redstone's health is said to have declined considerably since his last in-person interview, which THR published in January 2014. At that time, he was joined by Holland and Herzer and had to be supported by a male aide, even when he moved from one chair to another. Now sources say his speech is all but unintelligible. Within industry circles, eyebrows shot up when Viacom COO Tom Dooley was quoted in a recent Vanity Fair article saying that Redstone still was "sharp as a tack." ("Maybe he's used to tacks that aren't that sharp," snarks one company insider.)

Industry figures were equally surprised when the article reported that Redstone had answered the magazine's questions via emails, in which he claimed, "Every day I ride my bike and go to the pool." That seems a stretch for a man who has been using a feeding tube since September, according to one person who has seen him. A Viacom insider, however, says that Redstone's estate attorney Leah Bishoppersonally ensured the answers came from the mogul himself.

Bishop insists to THR that Redstone conveyed the responses in the emails. "I met with him," she says. "We went over them extensively. Those are his responses." While acknowledging that his speech is "severely impaired" and that he no longer can be understood on the phone, Bishop says "he can be clearly understood" in person. Did she feel obligated to verify the content of his assertions in the emails? "I am his estate planner," she replies. "When I am meeting with him on estate matters, I am responsible for the content. In this case, I simply needed to confirm that these were his responses."

Asked whether she had any comment on the credibility of his answers regarding his daily regimen, she says, "Of course not."

Redstone's National Amusements controls two giant, publicly held media companies, and the murk surrounding his health has been noted by analysts, none of whom wishes to be quoted on the record regarding the issue. One sums up the frustration, saying: "He is executive chairman of this company. The question someone needs to raise is: Is the board doing its duty? Is he capable of being an executive chairman of a public company right now?"

Vanity Fair reported that Redstone would attend the CBS annual shareholders meeting May 21. But on May 14, the company put out a statement from Redstone saying he would not attend, but adding, "I hope to attend next year's meeting." (Redstone was glimpsed fleetingly at last year's gathering, having been carried onstage in a chair.)

Much about Redstone, whose net worth fluctuates around $6 billion depending on the stock prices of CBS and Viacom, and the future of his empire remains unclear. But it is apparent that some people benefit more than others if the aged billionaire remains in control in his diminished state. Holland and Herzer are said to have reaped millions of dollars in gifts from their association with Redstone; and some believe a fight with Shari looms over his personal fortune.

The New York Post reported May 19 that it had obtained "explosive emails" between Holland and her attorney, Andrew Katzenstein of Proskauer Rose, who allegedly told her she already was "good for between $9 million and $10 million," in the phrasing of the article, which also stated: "The raven-haired temptress, who once ran a millionaire matchmaker firm, bragged to a lawyer in 2011 that she was getting a gorgeous diamond ring and was 'up to' $3 million in the will."

Holland's attorney Robert Shapiro tells THR via a statement that his client does not believe the emails are authentic, but some sources believe they might have been leaked from a laptop computer that Holland alleged in a lawsuit was "stolen" in 2013 by Heather Naylor, a onetime Redstone girlfriend who starred in the short-lived The Electric Barbarellas series on Viacom's MTV network. (That lawsuit settled in April, and, according to the court docket, Naylor now is seeking more than $11,000 in costs associated with the suit. Naylor's attorney Terese Beluris declined to comment on Naylor's role, if any, in the leak of the emails.)

In recent years, some observers believed that Philippe Dauman, president and CEO of Viacom, would control the seven-person trust that will oversee Redstone's controlling shares in the two companies. But now some insiders think Shari has a majority of votes — and she is not known to be a fan of Dauman. A Viacom source stresses that the trust members — including Shari's son Tyler Korff — all are lawyers who are aware of their obligations to act in the interest of the beneficiaries, Redstone's grandchildren. (Tyler Korff also is a rabbi.)

Dauman, 61, has been facing challenges as ratings and ad revenue at Viacom's cable networks have dropped and its stock has traded in the mid-$60s after reaching $89.76 in summer 2014. Perhaps Dauman can turn things around with time, but right now he doesn't appear to enjoy an advantage compared to CBS Corp. president and CEO Leslie Moonves, 65, who is said to be "very comfortable" with the idea that Shari might take control of the trust.

"Moonves is in a strong position," says analyst Harold Vogel. "In a challenging environment for broadcast television, he's done very well and has a lot of support on Wall Street. You don't have some of the complaints and challenges at CBS that you seem to have at Viacom."

When Redstone no longer is in the picture, Vogel thinks Viacom's stock could soar. "People know what the assets are. They know what the opportunities are," he says. "Under ordinary, logical, rational circumstances, you'd say the stock is going nowhere."

But some have speculated that buyers could line up for what analyst Michael Nathanson describes as "a cheap company with powerful brands." While much still is uncertain, Vogel says, "You know investment bankers are licking their chops to do some kind of deal with somebody at some point."